This experimental study was designed to evaluate the effect of planned teaching on the self-medication practices of ambulatory cardiac patients. The sample was composed of forty male and female cardiac patients who were over the age of forty-five years, who lived at home and were of low socio-economic status. They all lived in a large urban centre and attended an outpatient clinic for medical attention. All were taking digoxin and thirty-six, 18 from each group, were also taking a diuretic. They were randomly assigned to two groups, experimental and control, when they visited the outpatient clinic. The twenty patients in the control group were given the usual routine factual information during their clinic visit. The twenty patients in the experimental group received additional planned teaching over a thirty-minute period by the researcher. The data were gathered by means of a twenty-item questionnaire designed to elicit information regarding the self-medication behavior of the study population. The questionnaire was administered in the homes of the patients ten to fourteen days following their visit to the outpatient clinic. Three hypotheses were tested in the study. Analysis of the data in relation to Hypothesis I indicated a statistically significant difference in the number of self-medication errors in digoxin and diuretics made in a twenty-four-hour period by patients in the experimental group as compared with the control group. The experimental group made significantly fewer errors. Although patients in the experimental group made fewer errors of the four types of errors studied with regard to Hypothesis II, there was not a statistically significant difference in errors related to time, dosage and non-prescribed medications made in a twenty-four-hour period by patients in the experimental group as compared with the control group. There was, however, a statistically significant difference in the fourth type of error--that of omission. The testing of Hypothesis III showed a statistically significant difference in the level of knowledge of the two groups of patients. The experimental group had a higher level of knowledge of their medications. The study concludes with consideration of implications for nursing practice and research. / Applied Science, Faculty of / Nursing, School of / Graduate